[TowerTalk] am towers

[D.Calder]

I think we a "large" discount with the amount we do a year. I have to admit.
 
Dave
 
 
From: jim Jarvis [mailto:jimjarvis at optonline.net] 
Sent: Monday, February 16, 2009 8:15 AM
To: D.Calder; towertalk at contesting.com
Subject: Re: [TowerTalk] am towers
 
not what I meant, Don.
 
The tower is substantial.    Whatever 'proof' was performed was minimal, if
they only charged you $1200:
 
It really depends on the nature of the AM array.   If it were an omni
situation,
just taking a couple of readings at a mile would suffice.    If, however, it
was a
4 tower inline, where one of the towers had little or negative energy in it,
the
pattern could be easily disturbed.   In that case, a full proof could be
required.
It has to be done when there is no skywave.  Depending on Frequency, you
could
be limited to 10am to 2pm.    It takes a 2 man crew for each car, and you
might get in 
one radial a day, given 10 points, depending on terrain and roads and
weather. 
That's 20 man-days.   Plus the consulting engineer.   
 
When you take a f.s. reading,  you also have to take a picture, time
stamped.
This clearly identifies the measurement point, establishes the time line,
and gives a visual
record of environmental variables which may be around the point, disturbing 
the reading.    When the data is reduced, some points need to be discarded
as
useless, and replaced with others.  More driving, for repeat measurements. 
Although with computers it's fairly easy, now to reduce all readings, each
reading 
needs to be reduced to account for distance.
 
In a re-proof, to verify no change,  you could take a skeletal set of 
readings, looking for shifts in nulls.    So, you might start by taking
several readings
on radials each side of each null.   If the f.s. readings haven't changed,
then 
you could spot-check the main lobe(s), and in the center of each null.   If
they're
nominally ok, you're good to go.   THAT could be achieved in maybe two or
three days,
depending on weather and the number of towers.    At the current contract
rate for
a chief engineer,  call it 10-20 hours @ $65... no change found, and no
consultant required.  
Your $1200 figure is reasonable, under those conditions.    
 
n2ea



 
On Feb 16, 2009, at 7:02 AM, D.Calder wrote:



Putting up a 350' tower 1/4" mile from a AM station is nothing?
 
n4zkf